Viterbi equalisation of mobile radio channels having large delay spreads

Recent mobile radio systems, such as the GSM, advocate the use of time division multiple access (TDMA) where each TDMA signal is transmitted on a carrier frequency. The mobile user is allocated a time slot in a TDMA frame during which digital encoded data is transmitted at a high rate. The radio channel characteristics change significantly TDMA bursts as the mobile travels through a changing environment. Owing to the high transmission rate, fast fading and resolvable multipath phenomena are observed causing intersymbol interference (ISI) which may severely degrade the bit error rate (BER) performance. To ensure an acceptable BER, a channel equaliser is employed. In this paper, the authors consider the Viterbi equaliser (VE) which is a maximum likelihood sequence estimator in the strict sense